Apache log4net: Oversize EventLogAppender record silently discarded
Insufficient Logging vulnerability in the EventLogAppender of Apache log4net. Long messages were truncated to a fixed size that exceeds what the Windows Event Log accepts once the log and source names are counted, and the event log then stored nothing and reported nothing. A party whose data reaches a log message could suppress the whole record by making it long enough. Only applications on Windows that use EventLogAppender are affected. This issue affects Apache log4net: from 1.2.9 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.
CVE-2026-105243
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-105243
Apache log4net
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Apache log4net
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "Apache Software Foundation",
"product": "Apache log4net",
"versions": [
{
"status": "affected",
"version": "1.2.9",
"lessThan": "3.5.0",
"versionType": "semver"
}
],
"packageURL": "pkg:nuget/log4net",
"packageName": "log4net",
"collectionURL": "https://nuget.org/packages",
"defaultStatus": "unaffected"
},
{
"repo": "https://gitbox.apache.org/repos/asf/logging-log4net.git",
"vendor": "Apache Software Foundation",
"product": "Apache log4net",
"versions": [
{
"status": "affected",
"version": "02e1e115435888485f2e28b414d267e39e799e07",
"lessThan": "28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed",
"versionType": "git"
}
],
"packageURL": "pkg:nuget/log4net",
"packageName": "log4net",
"collectionURL": "https://nuget.org/packages",
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-105243
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #11894 · Revision 1
- Added to Heist Feed
- Publisher date